Can I pperate a telephone with a local power supply?

I'm planning on a project involving use of telephone. Now what I want to know is, whether it is possible to operate a telephone with a local power supply rather connecting to the copper wire pair from my PSTN operator. If yes at what voltage does a normal phone operate.
I only need to generate the DTMF signals from my phone.

Magnetra

Telephone

Here's some info that can get you started:
http://www.egyed.com/faq/phonework.html

Re: Telephone

Hmm, I went throught the article, it was informative.
I have a question, how does the received and transmitted voice signal travel over the same copper pair? Doesn't any interference occur?

Magnetra

Re: Telephone

magnetra said:

Hmm, I went throught the article, it was informative.
I have a question, how does the received and transmitted voice signal travel over the same copper pair? Doesn't any interference occur?

Magnetra

Click to expand...

Read more of telephone...

Phone using bridge to cancel voice from mic, but still hear opposite side voice

This network calling often for 'hybrid' or 'fork' (from symbol of this) in litterature (and very often skip describe inside of the 'box') and builds beginning based on transformer (even to days for simple, non thinking design) and now electroic version in most modern phone (this is _not_ easy to make, you need like analog design and understud transmission theory to design this).


This circurit is not perfectly matched to lines impedance and small pieces of sending voice always leaking back to earphone, more or less - and calling for 'side tone' in litterature ( take from leaking of 'unbalanced' balanced network)

Phone user not want perfect isolation (ie. not hering itself) and practical wanted leaking to earphone is 12 - 15 dB lower than sending level for comfortable hearing itself talking.

/xxargs